Troubleshooting Notes

on AirSport Altitude Alerter / Transponder Monitors

The most common problems involve
power.Some units are operated from the internal battery, others
run on aircraft power, some pilots use both. With few exceptions, if the power
is OK, the unit will function properly.

So what can go wrong with the power?Well, first let's consider the internal battery. It is a sealed lead-acid
battery, so the chemistry is very similar to a car or aircraft battery. The
worst thing that can happen is to discharge it completely and leave it that
way. This can happen if the unit is left on, for example. That is why
there is a battery switch on the rear panel. If the battery switch is off, then
the battery is completely disconnected. (Good for long term storage, for
example.)

It's not a good idea to discharge the battery completely, and if the
battery is discharged repeatedly it will be ruined. It's the same with a plane
or car battery. Don't take it all the way down. And when it is used, recharge
it as soon as practical. (Not next spring!)

Remember, the battery switch disconnects the battery. If the
switch is off, you cannot charge or use the battery. But the rear switch is not
the power switch. The power switch is on the front panel. Sometimes pilots turn
on the front switch, don't see anything, and then remember to turn on the
battery. This isn't the proper sequence. Here's why: When the Altitude Alerter
is turned on, it's computer "boots up". This is a start-up sequence that sets a
number of variables to the proper value. It happens when you flip the front
panel power switch on. If there is no power (because the battery switch is off)
then the boot sequence cannot occur. The answer: Be sure the battery switch
is on first, then turn on the front power switch.

That leads us to the next major problem area, aircraft power. If the
battery switch is on, then any momentary interruption of power from the
aircraft is not a problem, because the battery will carry the load during the
power glitch. But if the battery is not in use, then a momentary interruption
is the same as the previous paragraph, with the possibility of an incorrect
re-boot. The computer chip has a built-in "watchdog" function that usually
catches these problems, but occasionally a power interruption can result in a
blank display, or other difficulties.

Where do these interruptions come from?Usually the cigarette lighter is the culprit. It wasn't designed to be a
power source, it was designed to light cigarettes. A little corrosion can cause
a wide range of problems. If your alerter seems to go blank at odd times, or
has other strange symptoms, suspect the power source.

Our cigarette lighter cords are fused. The fuse is located in the
center pin of the large plug. To change the fuse, press the pin in, turn it
counter-clockwise about 45 degrees, and pull it out. The fuse can now be
removed. It should be a 3 amp fast-blow fuse, type 3AG. This is a common,
widely available fuse.

If the display goes blank, here's what to do.
Turn the unit off on the front. Also turn the battery switch off
on the back, and unplug the power cord if you are using one. Now wait for at
least three minutes, this is necessary to allow the internal circuits to
discharge. Then turn on the battery switch on the rear panel, and finally turn
on the front power switch. The sequence is important, the last thing to turn on
is the front switch.